Subsea Equipment

ABSTRACT

A subsea equipment ( 1 ) used for natural gas or crude oil production, such as a subsea actuator ( 2 ) for a valve, a restrictor or the like, a control module or other means, comprises at least an oil-filled first component ( 3 ) and a compensator unit ( 4 ) which is associated with said first component and which is in fluid communication therewith for pressure compensation. To improve such a subsea equipment in a structurally simple manner in such a way that it is capable of functioning and that pressure compensation is still possible, even if the associated compensator unit is damaged or fails to operate, a second compensator unit ( 5 ) is in fluid communication with said first component ( 3 ) or said first compensator unit ( 4 ) for pressure compensation.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a National Phase entry of PCT Application No.PCT/EP2005/011255 filed 19 Oct. 2005, hereby incorporated herein byreference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

The invention relates to a subsea equipment used for natural gas orcrude oil production, such as subsea actuators for a valves, restrictorsor the like, control modules, so-called BOP (blowout preventors), orother means, and comprising at least one closed, oil-filled firstcomponent and a first compensator unit which is associated with saidfirst component and which is in fluid communication therewith forpressure compensation,

Such subsea equipment is arranged in situ on the seabed, on a so-calledtree, on an oil platform and other components for natural gas or crudeoil production. A subsea actuator serves e.g. to adjust a valve or arestrictor so as to interrupt, or at least vary the flow throughrespective pipes. Also for the so-called blowout preventor, an actuatoris used. Such a blowout preventor serves to prevent, in emergency cases,crude oil or natural gas from escaping on the seabed from respectivepipes at the well.

In the case of a closed, oil-filled subsea equipment, a respectivecomponent has normally associated therewith a compensator unit forpressure compensation. Pressure compensation is effected between thecomponent and the environment, i.e. the water. The pressure compensatedis the hydrostatic pressure (water depth) and also pressure differencescaused by changes in temperature and/or volume. One example for a changein volume is here e.g. a piston which is movable in a cylinder.

In subsea equipments known in practice, a component or a plurality ofcomponents has associated therewith a respective compensator unit whichaccomplishes pressure compensation separately for the componentassociated therewith. If the compensator unit in question fails tooperate due to the occurrence of a leak or the like, the function of theassociated component will at least be impaired or the component willperhaps no longer be capable of functioning at all.

It is therefore the object of the present invention to improve a subseaequipment of the type referred to at the beginning in a structurallysimple manner in such a way that it is still capable of functioning andthat pressure compensation is still possible, even if the associatedcompensator unit is damaged or fails to operate. In connection with thefeatures of the generic clause of claim 1, this object is achieved inthat a second compensator unit is in fluid communication with the firstcomponent or the first compensator unit for pressure compensation.

BRIEF SUMMARY OF THE PREFERRED EMBODIMENTS

This can, on the one hand, be accomplished by a suitable connectionbetween the second compensator unit and the first component. This offersthe possibility of still using the second compensator unit for pressurecompensation if the first compensator unit should fail to operate. Inthis way, the two compensator units are independent from and redundantwith regard to one another.

On the other hand, there is the possibility of connecting the secondcompensator unit to the first compensator unit so that pressurecompensation is essentially effected via the first compensator unit bymeans of the second compensator unit.

In accordance with an advantageous embodiment of the present invention,the second compensator unit can be associated with a second closed,oil-filled component for pressure compensation. The second compensatorunit thus fulfils essentially a dual function in that it provides, onthe one hand, pressure compensation for the second component and allows,on the other hand, pressure compensation for the first component or thefirst compensator unit via the connection to said first component or tosaid first compensator unit, possibly in combination with said firstcompensator unit.

Various embodiments of the respective compensator units are imaginable.One example, which is used comparatively often in subsea equipments,makes use of a bladder accumulator as a compensator unit. Such a bladderaccumulator is used e.g. also as a pressure accumulator in hydraulicequipment. Such a bladder accumulator is essentially characterized inthat it utilizes a bladder or a membrane as a compensator element, saidbladder or membrane having on one side thereof seawater and on the otherside thereof a compensating fluid, such as a hydraulic fluid,transmission oil, a low-viscosity substance or the like. Thesesubstances will be referred to as hydraulic fluid in the following. Thepressure difference is compensated by contracting and expanding thebladder or the membrane. It is possible to realize one or both of saidcompensator units by such a bladder accumulator.

In accordance with a further embodiment, the first and/or secondcompensator unit(s) is/are implemented as piston accumulator(s). Such apiston accumulator comprises a piston which is longitudinallydisplaceable in a cylinder. The piston as such serves as a compensatorelement. Also in this case, seawater is on one side and hydraulic fluidon the other side of the piston.

It is also possible to implement the first and/or second compensatorunit(s) as pressure accumulator(s). Such a pressure accumulator has apressure fluid on one side of the compensator element, whereas on theother side of said compensator element there is again the hydraulicfluid. The pressure of the pressure fluid can be changed externally forpressure compensation, the amount of the pressure fluid being in thiscase increased or reduced.

Various embodiments of the first and also of the second component areimaginable. One example of the first and/or second component(s) is anactuator or a spring package. The actuator normally comprises adisplacement element which is adapted to be displaced for operating avalve, a restrictor or the like. The spring package is used e.g. inconnection with such an actuator so as to allow a definite startingposition of the actuator even if said actuator fails to operate, saidspring package being biased in the direction of this position.

Such a spring package is normally used with a bladder accumulator as acompensator unit. This bladder accumulator can be arranged externally ofsaid spring package in the sea-water surrounding the subsea equipment.

The actuator, which normally has an actuator housing, has associatedtherewith a bladder accumulator or a piston accumulator as a compensatorunit. Said compensator unit is arranged, at least partially, in theinterior of the actuator, i.e. of the housing of said actuator.

In order to establish the respective fluid connection, bores in theinterior of the subsea equipment are imaginable, said bores establishingthe fluid connection in question. For allowing more variations, thefluid connection can be implemented between the first compensator unitand the first component, the first compensator unit and/or the secondcompensator unit and/or the second compensator unit and the secondcomponent as respective hydraulic lines extending between the elementsin question.

The hydraulic lines may also extend, at least partially, outside of therespective subsea equipment.

Such a subsea equipment also uses components, such as an actuator, whichwould no longer be capable of functioning within a short time after theingress of water through the compensator unit, i.e. the actuator wouldhave to be removed and pulled to the surface, and another actuator wouldhave to be installed in the meantime, or the whole subsea equipmentwould not longer be capable of functioning. Water may ingress through aleak e.g. in the compensator unit. In addition, it turned out that,especially in the case of a piston accumulator, algae and sediment willgather within a short time on the compensator element side which is incontact with seawater. This will lead to a failure of the compensatorunit, i.e. the piston in question will no longer be displaceable so asto accomplish pressure compensation.

In accordance with the present invention it is possible that the sidelocated opposite the hydraulic side of the compensator element hassupplied thereto hydraulic fluid from the other component or from theother compensator unit so that there will be no seawater on this side,i.e. that at least in the case of the first compensator unit associatedwith the actuator hydraulic fluid is present on both sides of thecompensator element. This can be realized e.g. in that the respectivefluid connection terminates in the interior of the compensator unit onboth sides of the compensator element. The compensator element is thusconnected on one side thereof to the actuator for pressure compensation,whereas the other side of said compensator element is connected to theother component or the other, second compensator unit.

A gathering of algae or sediments will be prevented in this way and thecompensator unit will be protected against failure. Also an ingress ofwater into the actuator through the associated compensator unit will beprevented in this way. This will enhance the reliability of theactuator.

If the compensator unit of the actuator should fail to operate, noseawater can ingress into the actuator. Pressure compensation will thenbe taken over e.g. by the compensator unit of the spring package.

If the compensator unit of the spring package should fail to operate inthis connection, a direct ingress of water into the actuator isimpossible once more, and even the pressure compensation in the actuatorwill be maintained, since pressure compensation will still take placevia the respective fluid connection to the other component and to theother compensator unit, respectively.

If both compensator units should fail to operate, the seawater will haveto cover a long distance until it reaches the actuator. The seawaterwill first flow into the spring package through the spring-packagecompensator unit which is still in contact with seawater; in said springpackage a sufficient amount of seawater will have to gather and flowthen through the fluid connection to the first compensator unit andfinally up to the actuator. This is, however, a very long way, partlythrough tubing having a small cross-section and substantially withoutany pressure differences, so that also in this case, the actuator willstill be capable of operating for a long time and a failure of theactuator will normally be unlikely.

For reasons of redundancy, it is also possible to connect also in thisrespect at least one additional compensator unit in parallel with saidfirst and/or second compensator unit(s), this means that e.g. thecompensator unit associated with the spring package is implemented twiceand in parallel and/or that the compensator unit associated with theactuator is implemented twice and also in parallel. In the case of thecompensator units of the actuator the fluid connection to the othercomponent or to the other compensator unit or units is establishedaccordingly, as has already been explained hereinbefore.

A simple way of pressure compensation can also be accomplished without apressure accumulator with a respective pressure fluid by opening atleast one compensator unit on one side thereof towards the environment.The compensator unit in question is normally the second compensator unitwhich is not associated with the actuator, so as to prevent theabove-described ingress of water into the actuator as reliably aspossible.

It is, however, also possible that, contrary to the case where theactuator and the spring package are used, not both the componentscontribute to the function of the subsea equipment. If the twocompensator units are not directly connected to one another, they may,for example, also have arranged between them an oil-filled container asa component. Also in this respect it will be of advantage when thenfirst and second compensator units are connected in series.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, an advantageous embodiment of the present inventionwill be explained in detail on the basis of the FIGURES enclosed, inwhich:

FIG. 1 shows a side view, partly in section, of a subsea equipmentaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a side view, partly in section, of an embodiment of asubsea equipment 1 according to the present invention. This subseaequipment is implemented as a subsea actuator 2 with a spring package 10comprising a spring element 21 as a second component 6 and an actuator11 as a first component 3. The actuator 11 is electrically operated andis provided with a longitudinally displaceable operating element 18.This operating element 18 is shown in FIG. 1 in two different positions.In the upper half of the actuator 11, the operating element 18 isarranged at a retraced position at which a flow passage 22 through ahousing 24 is blocked by means of a suitable blocking element 23. In thelower half of FIG. 1, the operating element 18 has been displaced to theright of the figure and opens the flow passage 22 with the blockingelement 23.

Each of these components has associated therewith a compensator unit forpressure compensation. By means of this compensator unit, pressurecompensation is provided between the closed, oil-filled components andthe environment, i.e. seawater. What is compensated is the hydrostaticpressure corresponding to the water depth and also pressure differencesresulting from changes in temperature and/or volume, cf. e.g. thedisplacement of the operating element 18 in the longitudinal direction.

The first component 3, i.e. the actuator 11, has associated therewith abladder accumulator 7 as a first compensator unit 4. This bladderaccumulator 7 is in fluid communication with the interior of theactuator at one end thereof (not shown). The other end of the bladderaccumulator 7 is in fluid communication with the interior of the secondcomponent 6, i.e. the spring package 10, via an inlet 29 by means of ahydraulic line 12. Hence, the hydraulic line 12 terminates in theinterior of the spring package 10 via a connection 26. Adjacent to saidconnection 26, a connection 25 is arranged through which a fluidconnection is established between the second component 6 and a secondcompensator unit 5 by means of the hydraulic line 13. Also this secondcompensator unit 5 is implemented as a bladder accumulator.

It is possible to implement both bladder accumulators also as pressureaccumulators 9; in this case a suitable pressure fluid wouldadditionally be provided. The amount of said pressure fluid can becontrolled externally for varying the pressure and thus the pressurecompensation by means of the first and second components.

Normally, the second compensator unit 5 will, however, be open towardsthe seawater via an outlet 28.

In FIG. 1 a piston accumulator 8 acting as a first compensator unit 4 isshown, as an alternative, below the first compensator unit 4. Such apiston accumulator 8 comprises a piston 15 as a compensator element 14,said piston 15 being displaceably supported in a cylinder.

According to the present invention, hydraulic fluid is, also in the caseof the bladder accumulators 7, filled in on either side of therespective compensator element 14, i.e. the interior 16 of the firstcompensator unit 4 is exclusively filled with hydraulic fluid, butnot—not even on only one side of the compensator element 14—withseawater.

In FIG. 1, the interior 16 of the first compensator unit 4 is dividedinto a first side 19 and a second side 20 by the compensator element 14.This applies analogously also to the bladder accumulator. The secondside 20 contains a hydraulic fluid which is in fluid communication withthe actuator 11. The first side 19 contains hydraulic fluid which is influid communication with the second component 6 and the secondcompensator unit 5, respectively, via the inlet 27 and the respectivehydraulic line 12. In this way, at least the first compensator unit 4 isprevented from containing seawater therein. In a piston accumulator, theseawater may otherwise have the effect that algae or sediment willgather on the first side 19 of the interior 16. This may lead to afailure of the compensator unit. In addition, a leak in the compensatorunit may have the effect that seawater flows to the second side 20; suchingress of water would mean that, within a short time, the actuatorwould no longer be capable of functioning.

In FIG. 1, additional embodiments of the present invention are shown, ofthe broken lines indicating the hydraulic lines 12 and 13. In oneembodiment, a direct connection between the second compensator unit 5and the first compensator unit 4 can be established by the hydrauliclines 12 and 13. In this case, there would be no fluid connectionbetween the first compensator unit and the second component 6. Therespective fluid connection between the second component 6 and thesecond compensator unit 5 can, however, be maintained.

In a second embodiment, the second component 6 is not implemented as anactive component for the subsea equipment 1, but it is replaced by anoil-filled container 17 arranged between the hydraulic lines 12 and 13.This oil-filled container essentially serves as an intermediate storagemeans for the hydraulic fluid.

Reference is additionally made to the fact that it is also possible toconnect e.g. the first compensator unit 4 on its side 20 facing theactuator 3, 11 also, and instead of via the inlet 27, to the secondcomponent and the second compensator unit 5, respectively. This appliesanalogously, vice versa, also to the second compensator unit 5. Althoughthis means that a certain advantage with regard to the absence ofseawater in the first compensator unit 4 is given up, a redundantarrangement of the compensator units is obtained by the connection ofthe respective compensator units to the first and second components.

In addition, it is also possible to arrange, in addition to the firstand second compensator units, at least one additional compensator unit,which is e.g. redundant to the first or second compensator unit, in thatit is connected in parallel therewith, i.e. that, e.g. in addition tothe first compensator unit 4, the compensator unit 4 shown in the lowerhalf of FIG. 1 is actually used, and that both said compensator unitsare connected to the second component 6, the container 17 or the secondcompensator unit 5 via the hydraulic line 12. This applies analogouslyalso to the second compensator unit 5, which can also be provided as aredundant component and which can be connected to the second component 6or the container 17 via a respective hydraulic line 13.

1.-15. (canceled)
 16. A subsea actuator disposed in seawater comprising:a first component being closed and filled with oil; a first compensatorin fluid communication with said first component, said first compensatorcompensating the pressure between the oil within said first componentand the surrounding seawater; a second component being closed and filledwith oil; a second compensator in fluid communication with said secondcomponent, said second compensator compensating the pressure between theoil within said second component and the surrounding seawater; and ahydraulic line providing fluid communication between said firstcompensator and said second component.
 17. The subsea actuator of claim16, further comprising another hydraulic line providing fluidcommunication between said second compensator and said second component.18. The subsea actuator of claim 16, wherein at least one of said firstand second compensators is one of a group consisting of a bladderaccumulator, a piston accumulator, and a pressure accumulator.
 19. Thesubsea actuator of claim 16, wherein at least one of said first and saidsecond components is one of a group consisting of a spring package andan actuator.
 20. The subsea actuator of claim 16, wherein said secondcompensator is open to the surrounding seawater.
 21. The subsea actuatorof claim 16, wherein said first compensator includes a compensatorelement disposed therewithin, wherein the hydraulic line couples to afirst side of the compensator element and said first component couples asecond side of the compensator element.
 22. The subsea actuator of claim16, further comprising a third compensator connected in parallel withone of said first and second compensators.
 23. A subsea actuatorcomprising: a first component closed and filled with oil; a firstcompensator in fluid communication with said first component, said firstcompensator compensating the pressure between the oil within said firstcomponent and the surrounding seawater; a second component closed andfilled with oil; a second compensator in fluid communication with saidsecond component, said second compensator compensating f the pressurebetween the oil within said second component and surrounding seawater;and one or more hydraulic lines extending between said first compensatorand said second compensator.
 24. The subsea actuator of claim 23,further comprising a hydraulic line extending between said secondcompensator and said second component.
 25. The subsea actuator of claim23, wherein at least one of said first and second compensators is one ofa group consisting of a bladder accumulator, a piston accumulator, and apressure accumulator.
 26. The subsea actuator of claim 23, wherein atleast one of said first and second components is one of a groupconsisting of a spring package and an actuator.
 27. A subsea actuatorcomprising: a first component closed and filled with oil; a firstcompensator in fluid communication with said first component; a secondcomponent being a storage container; and a second compensator in fluidcommunication with said second component; wherein said first compensatorprovides pressure compensation between the oil within said firstcomponent and the surrounding seawater.
 28. The subsea actuator of claim27, further comprising a first hydraulic line extending between saidsecond component and said first compensator and a second hydraulic lineextending between said second component and said second compensator. 29.The subsea actuator of claim 28, wherein at least one of said first andsecond compensators is one of a group consisting of a bladderaccumulator, a piston accumulator, and a pressure accumulator.
 30. Thesubsea actuator of claim 28, wherein at least one of said first andsecond components is one of a group consisting of a spring package andan actuator.
 31. The subsea actuator of claim 27, further comprising athird compensator connected in parallel with one of said first andsecond compensators.